Ukip's most high-profile donor Arron Banks has backed Nigel Farage's former aide Raheem Kassam for the party leadership.
Mr Banks, an insurance tycoon and co-founder of the Leave.EU Brexit campaign, said his endorsement comes despite ex-deputy leader Paul Nuttall "running" for the job.
Mr Nuttall has yet to publicly declare if he will stand in the contest, having declined to stand in the previous leadership race earlier this year.
The current leadership contest was triggered after Diane James stepped down after just 18 days in charge.
Mr Kassam welcomed welcomed Mr Banks's support, saying: "This is a major endorsement from someone who has been one of the driving forces behind Ukip in recent years.
"Mr Banks ploughed his personal time and money into the referendum campaign and the party, and for those wondering whether he still stood with Ukip, this is a very clear sign: he does, under a Kassam leadership."
Mr Kassam added: "I'd like to thank Arron for the brave and important support, and I look forward to working with him to make Ukip great again."
Nominations to replace Ms James close on October 31. The new Ukip leader will be announced on November 28.